Try this as a last ditch attempt :
1) Right click on the setup file (assuming u have a full setup file on drive ~12.7Mb, if not download it from link posted by me some posts back) and click on properties.
2) Check the compatibility box, click apply then ok.
3) Run this setup and install it again.
http://img215.imageshack.us/img215/8297/compatibilityqj7.jpg